Ultrafast photoflash techniques are being used to study biological fluorescence probe molecules, and also to study the way that molecules and segments of macromolecules rotate in their biological microenvironment on the 10 to the minus 12th power - 10 to the minus 9th power sec timescale. Both intrinsic and extrinsic fluoroprobe molecules are being investigated, first to characterize fully the photophysics of these moieties, then later to utilize this information to study the nature of the microenvironments of these probes in biopolymers, proteins, and membranes. Primary emphasis will continue to be placed on the intrinsic probe tryptophan and extrinsic probes that are mainly homologs of anilino-napthalene-sulfonic-acid (ANS). As ubiquitous as these two types of fluoroprobes have been in biological studies, their photophysics has yet to be accurately characterized, greatly reducing their interpretive value. Measurements of microenvironmental effects on fluorescence lifetimes and rotational motions will lead to a better understanding of the structure-function relationship in biology.